class Solution {
public:
    int fib(int a) {
        if(a==0||a==1)return a;
        vector<int> hl;
        hl.push_back(0);
        hl.push_back(1);
        for(int i=2;i<n;i++) hl.push_back(hl[i-1]+hl[i-2]);
        return hl[a-1]+hl[a-2];
    }
};
